/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2000 Dan Papasian.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "compat.h"

#include <sys/param.h>
#include <sys/stat.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void usage(void);
static int print_matches(char *, char *);

static int silent;
static int allpaths;

int main(int argc, char **argv) {
  setprogname(argv[0]);
  char *p, *path;
  ssize_t pathlen;
  int opt, status;

  status = EXIT_SUCCESS;

  while ((opt = getopt(argc, argv, "as")) != -1) {
    switch (opt) {
      case 'a':
        allpaths = 1;
        break;
      case 's':
        silent = 1;
        break;
      default:
        usage();
        break;
    }
  }

  argv += optind;
  argc -= optind;

  if (argc == 0) usage();

  if ((p = getenv("PATH")) == NULL) exit(EXIT_FAILURE);
  pathlen = strlen(p) + 1;
  path = malloc(pathlen);
  if (path == NULL) err(EXIT_FAILURE, NULL);

  while (argc > 0) {
    memcpy(path, p, pathlen);

    if (strlen(*argv) >= FILENAME_MAX || print_matches(path, *argv) == -1)
      status = EXIT_FAILURE;

    argv++;
    argc--;
  }

  exit(status);
}

static void usage(void) {
  (void)fprintf(stderr, "usage: which [-as] program ...\n");
  exit(EXIT_FAILURE);
}

static int is_there(char *candidate) {
  struct stat fin;

  // NOTE: upstream had a workaround for false positives for root; for WASM this
  // doesn't make sense and breaks.
  if (access(candidate, X_OK) == 0 && stat(candidate, &fin) == 0 &&
      S_ISREG(fin.st_mode)) {
    if (!silent) printf("%s\n", candidate);
    return (1);
  }
  return (0);
}

static int print_matches(char *path, char *filename) {
  char candidate[PATH_MAX];
  const char *d;
  int found;

  if (strchr(filename, '/') != NULL) return (is_there(filename) ? 0 : -1);
  found = 0;
  while ((d = strsep(&path, ":")) != NULL) {
    if (*d == '\0') d = ".";
    if (snprintf(candidate, sizeof(candidate), "%s/%s", d, filename) >=
        (int)sizeof(candidate))
      continue;
    if (is_there(candidate)) {
      found = 1;
      if (!allpaths) break;
    }
  }
  return (found ? 0 : -1);
}
